The following publications are believed to represent the current state of the art:
U.S. Pat. Nos. 3,922,827 and 4,473,976;
Japanese Patent Publication Nos. 04189986, 06346634 and 2003027768;
German Patent Publication No. 10316405;
E. Heinle and F. Leonhardt, Towers: A Historical Survey, Butterworth Architecture, English translation, 1989, pp 98-99; and
Hyperboloid Structure, downloaded from http://en.wikipedia.org/wiki/Hyperboloid_structure on Jan. 27, 2012.